1. Field of the Invention
This invention relates to a pneumatic radial tire for airplanes comprising a belt comprised of plural belt plies each containing cords embedded therein in which these cords extending substantially zigzag in the circumferential direction of the belt ply while being axially bent at both side ends of the belt ply.
2. Description of the Related Art
As this type of the radial tire, there has hitherto been known a tire described, for example, in Japanese Utility Model laid open No. 48-96259. Such a tire comprises a belt comprised of plural belt plies each containing cords substantially uniformly embedded in the ply over a full width thereof to zigzag extend substantially in the circumferential direction while being axially bent at both side ends of the ply.
Since cut ends of the cords are not exposed at both side ends of the ply in such a radial tire, even when a cord angle of the ply with respect to an equatorial plane of the tire is made small for enhancing the total strength of the belt, the shearing strain between the plies at the belt end is small and the belt end separation hardly occurs. Consequently the total number of the belt plies can be reduced while maintaining a given safety level. Such a weight reduction of the belt can control the occurrence of a standing wave during running at a high speed on a runway through take off, so that the tire having the aforementioned belt plies can be said to be very suitable as a tire for airplanes.
However, when the belt is constructed only by piling a plurality of such belt plies one upon the other, if it is intended to run the tire at high speed after the tire is subjected to damage arriving at the inside of the belt, there is caused a problem that cracks are caused between belt plies in the vicinity of a deepest portion of such damage and grow. Finally a so-called cut peel off of scattering the belt and tread rubber around during running is caused. Therefore, such a belt ply is not used in the actual radial tires for airplanes though it has many merits.